Conveyor Belts

Understanding Conveyor Belt Calculations

Understanding a basic conveyor belt calculation will ensure your conveyor design is accurate and is not putting too many demands on your system.

Conveyor Calculations Legend

B: Sine of angle of incline
C: Center to center distance (inches)
D: Diameter of drive pulley (inches)
d: Diameter of tail pulley (inches)
E: Effective tension (lbs.)
E1: Slack side tension (lbs.)

E2: Tight side tension (lbs.)
F: Coefficient of friction (See Table #1)
G1: Load per square ft. (lbs.)
G2: Load per hour (lbs.)
HP: Horsepower
K: Drive Factor-see table #2

L: Belt length (inches)
M: Overall Belt Weight
P: Product weight (lbs.)
RPM: Revolutions per minute
S: Conveyor Speed-Feet per minute
T: Operating Tension PIW (lbs.)
W: Belt weight (inches)

Common Calculations for Proper Design

Belt Length

When the head and tail pulley are the same size: L=(D+d)/2 x 3.1416+2C
When one pulley is larger than the other pulley: L=(D+d)/2 x 3.1416+2C+(D-d)²/4c

Belt Speed

Expressed in feet per minute (FPM)

S=D x RPM x .2618 x 1.021

Belt Load

At one time when the load is known per square foot: P= G₁ x C(in feet)x W (in feet)
At one time when load is known by pounds per hour: P=G₂/(S x 60) x C(in feet)

Horsepower

Level Conveyors: HP=(F x S x (P+M))/33,000
Inclined Conveyors: HP=((P x B)+(P+M)x F x S)/33,000

Effective Tension

Pull needed to move belt and load horizontally: E= F x (P+M)

Tight Side Tension

Total tension to move belt and load horizontally: E₂= E+E₁

Slack Side Tension

Additional tension required to prevent slippage on drive pulley: E₁=E x K

Operating Tension

Determines the working strength of the belt to handle the job on per inch of width basis: T= E₂/W

The Coefficient of Friction

Belt	Steel of Aluminum	Metal Rollers
Friction surface on pulley side	.30 to .35	.10 to .15
Bare duck on pulley side	.20 to .25	.10 to .15
Cover on pulley side	.50 to .55	.10 to .15

The Drive Factor "K"

Belt wrap on drive pulley	Screw Take-Up	Gravity Take-Up
180°	Bare: 1.6 Lagged: 1.0	Bare: .84 Lagged: .50
220°	Bare: 1.2 Lagged: .6	Bare: .62 Lagged: .35
240°	Bare: 1.0 Lagged: .5	Bare: .54 Lagged: .30

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Speak With A Sparks Representative For Help With Your Conveyor Belt Calculations.